From the Civil War on, the South belonged to the Democrats out of pure hate for Lincoln and his Republican party. In '64, Lyndon Johnson knew that the Deomocrats support for the Civil rights would kill the solid south. Nixon too knew that Republicans could win the south by betraying Lincoln and re-enslaving southern blacks with the chains of Jim Crow.
This imbalance of power persisted as Ford, Reagan and the Bushes ran as righteous Christian enemies of American-Africans. Carter,of course provided a little comic relief in this American tragedy while Clinton proved that a figurative black man could be president as long as his sex drive didn't get literally out of control.
Enter Obama, a candidate much less Black than Bill Clinton but alot more Negro than Hillary. And the so-called solid south did the math and realized that Barack looked like the American south. The brick hard nut brittle of segragationist southern prejudice turned into a smooth bowl of golden brown grits named Obama.